1. Field of the Invention
The present invention relates to a sizing agent and to a recording sheet having the same to provide plain paper that is moderate in price and provides printed images having superior properties, such as good print density, color-forming properties, water-resistance, light-resistance, and non-bleeding. In particular, the invention provides plain paper suitable for ink-jet recording of full-color images.
2. Description of the Related Art
Ink-jet printers are widely used not only as output units of, for example, personal computers, but also as printing devices for printing on various kinds of materials. Ink used for ink-jet printers is generally composed of solutions produced by dissolving organic dyes into water and other solvents. The organic dyes include azo dyes, anthraquinone dyes, indigo dyes, phthalocyanine dyes, carbonium ion dyes, nitro dyes, quinoline dyes, and naphthoquinone dyes.
Printing on plain paper, which is a recording medium, using the above ink causes feathering, i.e., the deterioration of clear characters and images. Specifically, as the ink permeates, it bleeds along fibers in the paper. Unfortunately, the dots bleed severely and the periphery of the dots becomes jagged and blurred. Furthermore, the ink does not have sufficient water-resistance and light-resistance for recording images using ink-jet printers.
Dedicated coated paper having an ink-absorbing layer composed of a superabsorbent polymer thereon has been used in order to achieve clear color development and to prevent ink bleeding (see, for example, Japanese Patent Laid-Open Nos. 59-35977 and 1-135682). Unfortunately, because of the special coating, the paper is more costly to manufacture than plain paper, and lacks the texture that plain paper has. Accordingly, there has been an increased demand for low-cost plain paper for general purpose use in ink-jet printers.
In view of the above problems, plain paper for ink-jet recording is proposed, which has a coating solution applied to it. The coating solution comprises a cationic polymer, which is an active component, having a structure of (meth)acrylamide alkyl quaternary ammonium salt having a benzyl group, and a water-soluble resin (see, for example, Japanese Patent Laid-Open No. 10-119425).
However, in order to meet the recent demand for further improved ink durability, in particular, the demand for water-resistance and light-resistance of the ink for ink-jet recording of full-color images, further improvement in image-fastness is still desirable.